According to the CLI commands, Smart Accel is active on centrally managed SMBs. As i did configure it as locally Managed first, i am not sure if Smart Accel is enabled automatically when central management is used, but it seems logical. You can configure it using CLI, too !
I do not think that sk131852 suggests it is only supported for locally managed appliances at this time. According to marketing, this makes the Pro series faster, and it would be a very serious drawback if central management is slower than local management by 30% !
CCSP - CCSE / CCTE / CTPS / CCME / CCSM Elite / SMB Specialist